There's no good answer...

The weight of the plane is just one of many factors in engine selection.
Aircraft performance desired is important.
Structral integrity of the aircraft can limit the engine. (not good to have the engine pull the firewall out.)

Since you are looking for 3D performance... look at the expected finished weights of several kits, and look at thier engine recommendations. Note that for 3D sometimes the lighter bushing type engine will be used with a long low pitch prop, as top end rpm isn't a big deal, low airspeed and high thrust to weigh are what you want. Props are more efficient at lower rpm than what we commonly get out of engines such as the O.S. FX series. The weight savings of the bushing type can be a BIG 3D performance boost too. (reduced neeed for tail ballast... doubles the weight savings)